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Check out http://www.8020.net Their extrusions might be able to be incorporated into your concept.

Keep us posted as you progress.

Al

I work a lot with the 8020 products and it is fine for static displays and fixtures but I would advise against using it as part of a fixture that would be moved or have sliding / friction surfaces as the aluminum wears.

It is rigid but requires constant re-tightening and if things are moved about, the tend to "wiggle" the joints and things tend to wobble about after awhile.

I like your idea, you could probably get away with 1-1/4 into 1-1/2 tubing. its a bit loose but if you drilled some holes and welded some threaded nuts to the outer tube, you could thread in bolts to tighten up the table at whichever position you wanted. It kinda looks like you drew that in already. To reduce the risk of swayback you could opt to have your inner tubes be seperate pieces from your table frame which can simply be slipped through seperatly as you adjust your table, have them double up on each other for the entire length of the table (perhaps a shorter set for when you want the tables in the compact configuration)

Honestly though, I think you will end up spreading out the table to its entire length for 99% of your work and you will probably be wishing you made a 1 piece top for it.

Unless you need to fold it up and put the table aside after each project I think you will find yourself wanting a solid 1 piece flat table to work on.

Thanks for all the comments. There a lot to consider. I don't think I need to make the cross bars a perfect telescope fit if I have welded nuts for clamp bolts (I'm thinking 5/8" bolts) on the outside tubes. The bolts can take up a vertical gap (between inside and outside tubes), so I could weld the nuts on the side with the seam, and put the gap there. I'd want to crank the bolts pretty hard to keep things solid and prevent sagging, so another consideration is I don't want the bolts to crush the inside tubes or distort the outer ones. Not sure what thicknesses are required for that.

Most of the time, the limited space I have can't comfortably handle more than say a 32 x 42 table, but I'd like to make frames for benches and tables that might be 5ft by 3ft so it would be nice to clamp up the whole thing at once, and temporarily lose some room around the table. The posted ideas for add on or flip up side wings, or even separate tables, are something I need to consider.

The idea appeals to me, but I've found it not to be necessary to have a solid table top for fitup of larger projects.

I've often used sawhorses with two or three lengths of 3", 5# channel clamped at a right angle to them. The gaps between channels allow for access, and my clamp inventory is good enough most times to hold everything together for tack-up.

Ed's take is smart, especially from a KISS point of view. You could have the wings fold down, also. You could even have them swing up and lock into position with a gap between them and the main table, so you have an open slot for clamping whenever one of the wings is up and in position. A simple hinge is a lot easier to build than telescoping tubing -- easier to keep clean and functional, too.

Here's what I meant with my interlocking top idea. It would actually be two three-legged tables that would fit together. You could slide them apart for more surface area, and in doing so open up more clamping space as the table gets wider.

My idea is not smart, from a KISS point of view.

It would be tricky to cut, too, unless you used assorted rectangles to make each top.

I work a lot with the 8020 products and it is fine for static displays and fixtures but I would advise against using it as part of a fixture that would be moved or have sliding / friction surfaces as the aluminum wears.

It is rigid but requires constant re-tightening and if things are moved about, the tend to "wiggle" the joints and things tend to wobble about after awhile.

Thanks for the clarification. I have limited experience with the 80/20 but knew they did some linear stuff. Never considered the wear issues of the aluminum.

Of course you don't have the Open table design but I agree wid the others- lots o' work to make the Sliding Table, work.

i made my top out of 1"x1" sq tube (0.125" wall) spaced about 6"
apart. it's great for clamping things to. if i need a solid, flat,
surface, i just lay a piece of whatever is convenient and fits the bill
on top. even, on occasion, a piece of plywood

I would make the Main table solid and then just mount receiver tubes on the ends.

Yah, I kind of reached this conclusion after reading the 1st round of responses. Make one solid center table with 4 legs and no funny stuff. Have receiver tubes run side-to-side to accept wings, or a vise holder, or whatever else I dream up. I then have something simpler and sag-proof to start with, but has some expandability built in. I'll toss up another drawing soon.

I checked the price of hitch receiver tubing at local place, $114 for 6 feet. It sounds like a lot, but then I get to thinking that it's probably worth $50 (or whatever the cost is over seamed tubing) to not have to worry about the seam.